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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        var str = "hello"
        var char = str.charAt(0)//返回索引位置的字符
        console.log(char)
        console.log(str.charCodeAt(0))//返回unicode值
        console.log(String.fromCharCode(104))//对unicode值进行解码


        var a = "jo"
        var b = "pp"
        console.log(a.concat(b))//连接字符串

        var g = "hdahaihf"
        console.log(g.lastIndexOf('h'))//返回"h"在字符串中最后出现的位置

        var y = "hgaygdfddddddd"
        console.log(y.substring(1,3))//返回指定索引间的字符串不包括最后一个  slice()也行但其可以用负数
        

        var t = "jhjhh"
        console.log(t.toUpperCase())//转化为大写
        
    </script>
</body>
</html>